1. UNDERWATER WELDING
TECHNOLOGY ,ART , COURAGE
SHOBHIT ISHAN
474/09
SEMINAR ON
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2. • First under water welding by British
Admiralty – Dockyard
• In 1946, special waterproof electrodes were
developed in Holland by ‘Van der
Willingen’
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3. INTRODUCTION TO
UNDERWATER WELDING
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4. We cant lift ship and then repair it. Hence comes the use of underwater
welding
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5. •Wet welding
•Dry welding
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6. Hyperbaric welding is the process in which
a chamber is sealed around the structure to
be welded and is filled with a gas ( He and
Oxygen) at the prevailing pressure.
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7. Dry welding can be of two types
•Large habitat
•Mini habitat
Mini habitat for underwater welding.
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8. Large habitat for
underwater welding
Source: north stream
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Large habitat underwater welding

10. •Welder /diver safety
•Good weld quality
•Surface monitoring
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11. • Higher cost of process, training, etc
• Large quantity of costly and complex
equipments
• More deep, more energy requirement.
• Cant weld if weld spot is at
unreachable place
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12. • Simply means that job is
performed directly in the water
• It involves using special rod and
is similar to the process in
ordinary air welding
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14. ‹#›

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• WATER-------------HYDROGEN +
OXYGEN
• Dissolve in weld pool
• Solubility decrases and then comes out -
 porosity
• Oxygen as solid , liquid inclusions or
gases
• Hydrogen combines with oxygen forming
vapour

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Chemical composition

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Porosity-troubleshooted by including Calcium
carbonate

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•Microstructure
•Mechanical
properties

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• Effect of alloying elements on weld metal
microstructure and properties
• Managanese
• Boron and titanium
• Rare earth metals

20. • Cheapest
• Fastest
• Tensile strength is high
• Ease of access the weld spot
• No waste of time in constructing habitat
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21. • Rapid quenching decreases impact
strength, Ductility.
• Hydrogen embrittlement.
• Poor visibility in water.
• Higher energy density of
hydrogen, higher efficiency.
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22. • Power supply requrements-400 amp or larger.
DC generators, motor generators and rectifiers
are acceptable power supplies
• Power converters.
• Welding Generator, Pre-Setup
• Polarity.
• Diesel Driven Welding Generator Amperage
and Voltage settings.
• Gas Manifolds.
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23. • Underwater Oxygen-Arc Welding
Torches.-
Collet or grip
Oxygen valve
Flash arrester
• Waterproofing Surface Electrodes.
Epoxy 152
Lee lac 30-l2093
Polyurethane
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Figure showing schematic diagram for
underwater welding or cutting

25. • Hydrogen and oxygen are dissociated
from the water and will travel separately
as bubbles
• Oxygen cutting is about 60 percent
efficient
• Above river beds, especially in mud,
because trapped methane gas in the
proper concentrations can explode.
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26. • There is a risk to the welder/diver of electric
shock.
• There is a risk that defects may remain
undetected
• The other main area of risk is to the life or
health of the welder/diver from nitrogen
introduced into the blood steam during exposure
to air at increased pressure
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27. • Start cutting at the highest point and work
downward
• By withdrawing the electrode every few
seconds to allow water to enter the cut
• Gases may be vented to the surface with a vent
tube (flexible hose) secured in place from the
high point where gases would collect to a
position above the waterline.
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28. • Precautions include achieving adequate
electrical insulation of the welding
equipment
• Areas and voids must be vented or made
inert
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29. • Development of alternative welding methods
like friction welding, explosive welding, and
stud welding.
• Present trend is towards automation. THOR – 1
(TIG Hyperbaric Orbital Robot) is developed
where diver performs pipefitting, installs the
track and orbital head on the pipe and the rest
process is automated.
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